Possible Late Pleistocene Uplift Chesapeake Bay Entrance
Abstract
Paleontological and lithological studies of engineering borings and boring logs indicate that a buried, subaerial erosion surface of Pliocene (?)-Pleistocene age cuts across elastic sediments of pre-Yorktownian Miocene age in the subsurface and subbottom of the lower Chesapeake Bay area. When the bore-hole data are coupled with the results of subbottom echo profiling and pile driving records, it is possible to construct accurate cross sections of the buried Miocene-Pleistocene contact. The cross sections show "lows" in the erosion surface that may be correlated with the buried channels of the Pleistocene Elizabeth, James, York, and Susquehanna river valleys. Probable channel depths below mean low water at control points are: 100 feet (Elizabeth River, beneath Tunnel no. 1), 155 feet (James River, at Hampton Roads Tunnel), 120 feet (York River, at Yorktown), 158 feet (Susquehanna River, off Cape Charles City), and 160 feet (Susquehanna River, at Fisherman Island, Cape Charles). The channel depths of what is believed to be the buried Susquehanna River valley are less than expected when placed on a curve showing the expectable gradients of that stream during the time of the most-recent, maximum lowering of sea level (ca. 18,000 years B.P.). The discrepancy suggests uplift of that channel of approximately 170 feet in about the last 18,000 years (....)
